The invention relates to a method of forming a packaged semiconductor device and the resulting structure.
In some types of semiconductor die packaging a die is secured to the surface of a die support structure. Electrical connections are made between the die and the support structure. The die, electrical connections, and at least a part of the support structure are covered with an encapsulating material to form a semiconductor package. Leads extend from the package for electrical connection to any external circuit. The package is generally secured to a printed circuit board or other mounting substrate when in use. One method of reducing the thickness of a conventional semiconductor device package is to use a thin die support structure. A thin support structure is generally about 50 microns to 75 microns thick while a conventional support structure is typically about 200 microns thick. However, a thin support structure is typically about 100% more expensive than a conventional thicker structure and thus increases the cost of packaged semiconductor devices. Another disadvantage of a thin support structure is that during fabrication the thin structure flexes and/or bows more than a thicker structure. This bowing or flexing can weaken the strength of the die""s attachment to the structure as well as damage fragile electrical contacts between the die and support structure.
Yet another disadvantage of a thin support structure is its limited ability to secure and support multiple dice on a single support structure. One method of constructing multiple die assemblies on a conventional support structure is to stack dice vertically. U.S. Pat. No. 5,994,166 issued Nov. 30, 1999, to Salman Akram and Jerry M. Brooks discloses a semiconductor package with two die vertically stacked on opposing sides of a substrate. However, if multiple semiconductor dice are vertically stacked on a substrate the height of the packaged semiconductor devices increases. If on the other hand, multiple semiconductor dice are mounted horizontally side by side on a support structure, both the thickness and area of the support structure must be increased to support the multiple dice which results in larger packaged semiconductor devices. Thus, conventional techniques for securing multiple dice to a single support structure increase the dimensions of packaged semiconductor devices. It would be advantageous to have a semiconductor support structure that can secure and support multiple semiconductor dice which will results in a smaller dimensions semiconductor packages than conventional techniques while reducing the cost of the die support structure.
The invention provides a packaged semiconductor structure in which multiple semiconductor dice are secured to a common support structure. In an exemplary embodiment, a multi-layered support structure is formed. The support structure has a central cavity with an open surface at the top and a die support bottom surface. An aperture with a perimeter smaller than that of the central cavity is formed from the bottom exterior of the support structure to the central cavity. A first semiconductor die is supported and secured to the cavity bottom surface. The first die is electrically connected to the bottom surface of the support structure by electrical connections, e.g., wire bonds, which extend from the die through the aperture to electrical contact areas on the bottom exterior surface of the support structure. A second semiconductor die is secured on the top surface of the support structure and electrical connections are made between the second die and electrical contact areas on the bottom exterior surface of the support structure. The dice, electrical connections and structure cavity are encapsulated with encapsulating material to form a packaged semiconductor assembly.